In recent years, Patent Document 1 (Japanese Unexamined Patent Publication No. 2013-242763) discloses a conversation device that converses with a driver who drives a vehicle. The conversation device includes a storage unit that stores a candidate having contents of conversation with the driver, a conversation effect indicating the degree of improvement in the concentration level of the driver on driving, and the driver's preference in association with each other. The conversation device converses with the driver in accordance with the conversation contents corresponding to a candidate selected on the basis of the conversation effect and the preference, to thereby improve the degree of concentration of the driver on driving.